The invention relates to a compressor with a hypotrochoidal design having a rotor housing in which a circular piston rotor circulates. The compressor is mounted on a hollow eccentric shaft that is provided with an inlet opening limited in the circumferential direction by a control edge that runs essentially in the axial direction and determines the beginning of intake and the beginning of compression. Radial intake ducts of the circular piston rotor are associated with the opening. The radial intake ducts terminate in chambers formed between the circular piston rotor and the rotor housing. The rotor housing is provided in the vicinity of these chambers with outlet openings controlled by pressure valves.
A known compressor of the above-mentioned type has been used previously as an air pump. Its delivery is directly dependent upon the drive rpm at which the eccentric shaft is driven. High drive rpm values result in a correspondingly high delivery, while low drive rpm values produce a correspondingly low delivery.
Similar behavior has been exhibited by formerly conventional coolant compressors, in which the delivery of coolant was likewise directly dependent on the drive rpm, i.e. the current engine rpm. Since this direct dependence is unsatisfactory for both driving comfort and for the efficiency of an air conditioner in a motor vehicle, the motor vehicle industry now requires that delivery in coolant compressors be variable independently of the current drive rpm, e.g. that it remain constant while the rpm changes. In practice, this behavior can be achieved only in swashplate reciprocating compressors in which, by virtue of different diagonal positions of the swashplate, the piston travel and hence the delivery or throughput can be varied.
There is therefore needed a compressor with a hypotrochoidal design constructed such that its delivery does not depend solely on the drive rpm but can be kept constant or varied independently of the drive rpm.
These needs are achieved by providing a device for changing, in the circumferential direction, the angular position of the controlling edge of the inlet opening of the eccentric shaft that determines the beginning of compression for the compressor.
This design makes it possible, by changing the angular position of the controlling edge that determines the beginning of compression, to change the degree of filling of the individual chambers so that the delivery or throughput is changed as well. It can be expected that such a compressor with a hypotrochoidal design has considerable advantages over known swashplate reciprocating compressors with variable swashplate positions, since no reciprocating masses are required so that much higher rpm values are possible, and manufacture is cheaper.
In another embodiment of the present invention, the compressor is provided with a device, independent of the rpm of the eccentric shaft, for changing the angular position of the controlling edge of the inlet opening that determines the beginning of compression. In this way, the delivery of the compressor can be regulated in such fashion that it remains constant regardless of the rpm.
In one advantageous embodiment, the inlet opening is subdivided in the axial direction into two sections, one of which is provided in the eccentric shaft while the other is located in a sleeve that is mounted to rotate freely in the circumferential direction on the eccentric shaft. By rotating this, sleeve relative to the eccentric shaft, the angular position of the control edge that determines the beginning of compression can be changed relatively easily.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.